Does anyone know what the best fluid simulating software out there is? I don't know much about these products. I've heard that Realflow is the best but it is not for sale currently so that doesn't help unless you know when it will be released.
Lightwave and Maya both have good plug-ins. Blender has a very powerful fluid simulator, especially when you consider that the program is free. There are some pure vector programs which use wireframe representation.
Or there's Powder Game, which uses a fluid sim to represent air currents. Liquid Webtoy uses fluid simulations to sim liquids.
Powder Game:
http://dan-ball.jp/en/javagame/dust/
Liquid Webtoy:
http://dan-ball.jp/en/javagame/mc/
you can buy RealFlow here:
https://www.nextlimit.com/newtpv/?product=real_flow
it really depends on what kind of fluids you want to do...open ocean? river? pouring into a glass? etc...
in addition to the other suggestions you can have a look at Houdini - the Apprentice version is free: http://www.sidefx.com/index.php?option=com_content&task=view&id=589&Itemid=221